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RESEARCH Open Access
Insurance type and sepsis-associated
hospitalizations and sepsis-associated mortality
among US adults: A retrospective cohort study
James M O’Brien Jr
1*
,BoLu
2
, Naeem A Ali
1
, Deborah A Levine
2,3
, Scott K Aberegg
1
and Stanley Lemeshow
2
Abstract
Introduction: Socio-demographic and clinical factors associated with increased sepsis risk, including older age,
non-white race and specific co-morbidities, are more common among patients with Medicare or Medicaid or no
health insurance. We hypothesized that patients with Medicare and/or Medicaid or without health insurance have
a higher risk of sepsis-associated hospitalization or sepsis-associated death than those with private health insurance.
Methods: We performed a retrospective cohort study of records from the 2003 Nationwide Inpatient Sample. We
stratified the study cohort by Medicare age-qualification (18 to 64 and 65+ years old). We examined the association
between insurance category and sepsis diagnosis and death among admissions involving sepsis. We used validated
diagnostic codes to determine the presence of sepsis, co-morbidities and organ dysfunction and to provide risk-
adjustment.
Results: Among patients 18 to 64 years old, those with Medicaid (adjusted odds ratio (AOR) 1.50), Medicare (AOR
1.96), Medicaid + Medicare (AOR 2.22) and the uninsured (AOR 1.18) had significantly higher risk-adjusted odds of a
sepsis-associated admission than those with private insurance (all P < 0.0001). Those with Medicaid (AOR 1.17, P <
0.001) and those without insurance (AOR 1.45, P < 0.001) also had significantly higher adjusted odds of sepsis-
associated hospital mortality than those with private insurance. Among those 65+ years old, those with Medicaid

(AOR 1.43), Medicare alone (AOR 1.13) or Medicaid + Medicare (AOR 1.62) had significantly higher risk-adjusted odds
of sepsis-associated admission than those with private insurance and Medicare (all P < 0.0001). Among sepsis
patients 65+, uninsured patients had significantly higher risk-adjusted odds (AOR 1.45, P = 0.0048) and those with
Medicare alone had significantly lower risk-adjusted odds (AOR 0.92, P = 0.0072) of hospital mortality than those with
private insurance and Medicare. Lack of health insurance remained associated with sepsis-associated mortality after
stratification of hospitals into quartiles based on rates of sepsis-associated admissions or mortality in both age strata.
Conclusions: Risks of sepsis-associated hospitalization and sepsis-associated death vary by insurance. These
increased risks were not fully explained by the available socio-demographic factors, co-morbidities or hospital rates
of sepsis-related admissions or deaths.
Introduction
Sepsis is a common c ause of hospi talization and inten-
sive care unit admission. In 1995, there were approxi-
mately 750,000 cases of sepsis in the United States (US)
with a 30% mortality rate during hospitalization, result-
ing in 215,000 deaths annually [1]. Costs of sepsis-
related hospitalizatio ns were considerable with direct
costs of $16 billion [1]. These estim ates did not include
the costs of post-hospital care, of lost employment or of
informal care-giver assistance. Because of the numbers
of people affected and costs involved, sepsis is a condi-
tion which warrants attention from insurers as a target
to improve outcomes f or their enrollees and to contain
health care costs.
Some risk factors for sepsis and sepsis-rel ated mortal-
ity, including older age, non-white race, and specific co-
morbidities, are more common among patients with
* Correspondence:
1
Department of Internal Medicine, Division of Pulmonary, Allergy, Critical
Care and Sleep Medicine, Center for Critical Care, The Ohio State University

Medical Center, 201 Davis HLRI, Columbus, OH 43221, USA
Full list of author information is available at the end of the article
O’Brien et al. Critical Care 2011, 15:R130
/>© 2011 O’Brien et al .; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons
Attribution License (http://creati vecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in
any me dium, provided the original work is properl y cited.
Medica re and/or Medicaid or no health insurance [2,3].
Differences in insurance coverage may also be associated
with risk of sepsis or sepsis-related mortality because of
differences in access to care, disparities in provided care,
overall health status or other unknown factors. An asso-
ciation between insurance coverage and sepsis may pro-
vide incentive for payers to target sepsis as a disease for
organized intervention, such as value-based purchasing
utilizing performance measures, such as time-to-antibio-
tic administration for septic shock patients [4]. Further-
more, an association between insurance coverage and
sepsis, which is independent of known risk factors,
would call attention to these disparities in risk for sepsis
and poorer outcomes from sepsis among those without
private insurance and exploration of the mechanism of
such a relationship to identify modifiable factors.
Using nationally representative hospital-based data, we
assessed the association between health insurance type
and sepsis-related hospitalizations and sepsis-related
mortality. We hypothesized that those with Medicare
and/or Medicaid and those without health insurance
would have higher adjusted odds of sepsis and sepsis-
related death than patients with private health
insurance.

Materials and methods
Ethics statement
Because the Nation wide Inpatient Sample do es not
include any patient identifiers, the Ohio State University
Institutional Review Board waived the requirement of
review and consent.
Data source
This study utilized data from the 2003 version of the
Nationwide Inpatient Sample (NIS) [5], the largest all-
payer inpatient care database in the US. It contains data
which approximat e a 20% stratified sample of US hospi-
tals, including private, public and academic hospitals.
Weights are provided for each year of the database to
allow for calculation of national estimates of all hospita-
lizations. We included only adult records (≥18 years old)
with payer information. To reduce the likelihood of a
single hospitalization appearing in the study multiple
times and t ransfer bias [6], we excluded records whose
admission source was listed as “ano ther hospital” and
those with a discharge status of “transfer to a short term
hospital”.
Definitions
Because Medicare has an age-specific qualification, we
stratified analyses by patient age (18 to 64 and 65+
years old). The insurance category was recoded from the
primary and secondary payers abstracted from the NIS
record, which was prov ided by state-specific sources [7].
Because of variations by state in coding procedures, we
excluded records with either primary or secondary
payers coded as “no charge” (approximately 0.3% of all

records in the database) or “other” (3.2% of records in
the database). For the younger age-stratum (18 to 64
years old), records with Medicaid and Medicare listed as
primary and secondary payer (or vice versa) were cate-
gorized as “M edicaid + Medicare. ” The remai ning
records with Medicare as a primary o r secondary payer
were categorized as “Medicare,” regardless if they had
additional private insurance. Finally, remaining records
were classified as “Private Insurance”, “Medicaid” or
“Unins ured” as appropriate. For the older age-stratum
(65+ years old), “ Medicaid + Medicare” was categorized
as for the younger age stratum. Remaining records with
Medicare as a payer were categorized as either “Medi-
care alone” or “Private Insurance plus Medicare” if there
was no additional listed payer or if commercial insur-
ance was also listed, respectively. Remaining patients
were categorized as “Medicaid” or “Uninsured” as
appropriate. The reference group was “Private Insur-
ance” for the younger age-stratum and “Private Insur-
ance plus Medicare” for the older age stratum.
For the analyses examining sepsis-associated hospitali-
zation, we based the diagnosis of sepsis upon validat ed
ICD-9 codes [8], namely, if the discharge record con-
tained one or more codes for sepsis (038 (septicemia),
020.0 (septicemic), 790.7 (bacteremia), 117.9 (dissemi-
nated fungal infection), 112.5 (disseminated candida
infection), and 112.81 (disseminated fungal endocarditis)
as a primary or secondary diagnosis. Organ dysfunction
was defined as the presence of previously validated and
utilized ICD-9 and/or Current Procedural Terminology

Codes (CPT) [8,9]. For the analyses examining sepsis-
associated mortality, we analyzed only those records
with a qualifying sepsis ICD-9 and considered the
patien t to have died in the hospital if the discharge dis-
position indicated the patient had died.
Statistical analyses
We generated descriptive statistics reg arding the num-
ber of admissions and those associated with sepsis,
severe sepsis and sepsis-associated deaths. We also
report length of stay for these admissions.
Because age is a qualifying criterion for Medicare
eligibility and is also associated with sepsis risk, we
performed analyses by age-strata (18 to 64 years and
65+ years). First, we estimated the unadjusted associa-
tion between insurance category and sepsis within each
age-stratum. We used multivariable logistic regression
to adjust for known risk factors for seps is, including
demographic information [8,10]) and conditions asso-
ciated with increased sepsis risk [9,11-15], based on
ICD-9 and/or CPT codes. In instances in which patient
O’Brien et al. Critical Care 2011, 15:R130
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race was absent (approximately 25% of records), we
recoded race as “missing” andincludedtherecordin
analyses. We also included a co-morbidity index
(Charlson-Deyo score [16]), categorized based on preli-
minary analysis determining best fit with the odds of
sepsis. Because individual hospitals contribute multiple
records, design-based adjustments are used to provide
valid estimates accounting for the correlation among

records from the same hospital. Hospitals were identi-
fied as clusters in all analyses, as recommended in the
HCUP method report [17].
For the analyses of sepsis-associated death, we
included only sepsis-associated admissions and consid-
ered hospital mortality the dependent variable. Unad-
justed odds were estimated between insurance category
and mortality by age stratum. We constructed a risk-
adjusting model including demographic information,
Charlson-Deyo score, and the number of dysfunctional
organ systems for each age stratum. The number of dys-
functional organ systems was categorized as none, one,
or two or more, based on preliminary analysis of odds
of sepsis-associated death. We developed a final risk-
adjusting model using these covariates and adding sep-
sis-associated co-morbidities that altered the point esti-
mate of the adjusted odds ratio of any of the insurance
categories by ≥15% and/or that had a statistically signifi-
cant association (Wald P < 0.05) with sepsis-associated
mortality.
We assessed whether the association between lack of
health insurance and sepsis-associated mortality was
consistent within strata based on hospital sepsis volume
or hospital sepsis-associated mortality rates. Hospitals
with fewer than 20 sepsis-related admissions were
excluded from these analyses. We performed analyses
separately within strata based on quartiles of hospital-
based sepsis-associated admission rates (that is, the pro-
portion of total ad missions involving sepsis) or within
strata based on hospital-based sepsis-associated mortal-

ity rates (that is, the percentage of sepsis patients dying
in the hospital). In each analysis, we combined the mid-
dle two quartiles of hospitals to produce three strata of
hospitals (for example, the highest quartile of sepsis-
associated admission rates, middle quartiles of sepsis-
associated admission rates, and lowest quartile of sepsis-
associated admission rates). To account for the influence
of lack of insurance on sepsis-related mortality due to
fact ors other than the overall performance of the hospi-
tal, we ranked hospitals by sepsis-associated mortality
rate among patients with insurance (for example,
excluding uninsured patients). After stratifying hospitals,
subjects without insurance were then included in the
datasets for analysis.
We refit the final age-stratum-specific risk-adjusting
models developed as described previously for each
group, which was now divided both by age group and
by hospital strata, defined either by sepsis-associated
admission rate or mortality rate. If the association
between lack of insuran ce and sepsis-asso ciated mortal-
ity was due to uninsured patients receiving care in hos-
pitals with different rates of sepsis or sepsis-associated
mortality, we anticipated that the observed association
would be lost once the analyses adjusted for these
differences.
To assess any ef fect of discharge bias due to lack of
insurance on sepsis-associated mortality, we re-esti-
mated the odds ratio for uninsured patients, compared
to patients with private insurance assuming a mortality
rate of 10 to 50% among patients discharged to skilled

nursing and intermediate care facilities. Because the
sampling strategy was not stratified based on insurance
category, we did not risk-adjust these estimates.
All analyses were performed using survey-weight-
adjusting procedures in SAS 9.1 (SAS Institute, Inc.,
Cary, NC, USA). We used two-sided alpha values and
considered a P-value <0.05 to be statistically significant.
Portions of these analyses were presented in part at
the 2008 American Thorac ic Society Inte rnational Con-
ference and summary statistics are included in a sys-
tematic review [18].
Results
Insurance category and sepsis
In 2003, sepsis was involved in 1 in 35 admissions
(2.9%) and consumed 1 in 13 hospital days (7.7%). Of
these admissions, 52.7% were associated with organ fail-
ure(forexample,severesepsis)and14.8%hadasso-
ciated shock. Among sepsis patients, 20.6% died during
hospitalization, accounting for 1 in 4.3 of all deaths dur-
ing hospitalization (23.2%).
Tables 1 and 2 show the differences in age, race and
co-morbidities between the insurance ca tegories for
those18to64and65+yearsold,respectively.As
expected, Medicare was a more common form of insur-
ance among those 65+ and Medicaid alone (1.6%) and
Uninsured (0.3%) patients were uncommon among the
older age stratum. Sepsis-associated admissions were
more frequent among those 65+ (4.3% of hospitaliza-
tions) than those 18 to 64 (1.9%). Among patients 18 to
64 years old, patients with Medicare with or without

Medicaid had the highest percentage of hospital admis-
sions which were sepsis-associated (4.6% for each insur-
ance category). Among those 65+, the highest
percentages of sepsis-associated admissions were
observed in those with Medicaid + Medicare (6.4%) and
those with Medicaid alone (5.8%). In both age strata, the
patients with private insurance had the lowest percen-
tage of sepsis-associated admissions (1.4% in 18 to 64
years and 3.8% in 65+ years), but the observed rates
O’Brien et al. Critical Care 2011, 15:R130
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were similar to those in the uninsured patients. As
shown in Table 3, sepsis-associated admissions were
older, more commonly men, and had higher rates of
sepsis-associated co-morbidities.
Table 4 displays the age-strata-specific unadjusted and
risk-adjusted association between insurance group and
sepsis-associated hospitalization. In the younger age
stratum, when compared to those with private insur-
ance, all o ther insurance groups had significantly higher
unadjusted and adjusted odds of a sepsis-associated hos-
pitalization. The increase in risk-adjusted odds were
most pronounced among those with Medicaid + Medi-
care (adjusted odds ratio 2.22, P < 0.0001) and among
those with Medicare (AOR 1.96, P < 0.0001). In the
older age stratum, those with Medicaid + Medicare
(AOR 1.62, P < 0.0001), Medicaid alone (AOR 1.43, P <
0.0001) and Medicare alone (AOR 1.13, P < 0.0001) had
significantly higher risk-adjusted odds of a sepsis-asso-
ciated hospitalization than those with private insurance

plus Medicare. Uninsured patients had risk-adjusted
odds of sepsis-associated hospitalization similar to that
seen in the reference group.
Table 1 Insurance category and covariates of interest, 18 to 64 years old
Medicaid Medicare Medicaid + Medicare Uninsured Private insurance
Admissions, 10
3
(%) 3,920.6 (23.6%) 1,673.9 (10.1%) 537.0 (3.2%) 1,206.5 (7.3%) 9,260.6 (55.8%)
Age, Mean (95% C.I.) 35.5 (35.2 to 35.9) 51.2 (50.9 to 51.6) 48.5 (48.2 to 48.8) 39.3 (39.1 to 39.5) 42.2 (42.0 to 42.5)
Female, 10
3
(% of admissions) 2,975.5 (76.1%) 810.2 (48.5%) 292.4 (54.5%) 586.6 (48.3%) 6,187.8 (67.1%)
Race, 10
3
(% of admissions)
White 1,246.8 (31.8%) 792.2 (47.3%) 226.7 (42.2%) 486.6 (39.9%) 4,678.4 (51.5%)
Black 735.3 (18.8%) 263.8 (15.8%) 108.8 (20.3%) 196.7 (16.2%) 775.2 (8.4%)
Hispanic 812.9 (20.7%) 111.9 (6.7%) 35.7 (6.7%) 180.1 (14.8%) 635.2 (6.9%)
Asian or Pacific Islander 73.7 (1.9%) 15.1 (0.9%) 1.7 (0.3%) 17.1 (1.4%) 202.2 (2.2%)
Native American 9.6 (0.2%) 2.6 (0.2%) 1.1 (0.2%) 3.1 (0.3%) 13.9 (0.2%)
Other 112.9 (2.9%) 20.8 (1.2%) 8.7 (1.6%) 48.5 (4.0%) 202.5 (2.2%)
Missing 929.2 (23.7%) 467.5 (27.9%) 154.3 (28.7%) 286.1 (23.5%) 2,663.2 (28.8%)
Quartile of median annual household income by zip code, 10
3
(% of admissions)
<$36,000 1,681.4 (43.9%) 553.4 (34.1%) 225.0 (43.0%) 407.0 (34.8%) 1,684.0 (18.6%)
$36,000 to <$45,000 1,084.6 (28.3%) 470.7 (29.0%) 142.1 (27.2%) 352.1 (30.1%) 2,176.6 (24.0%)
$45,000 to <$60,000 733.3 (19.1%) 360.0 (22.2%) 102.7 (19.6%) 258.5 (22.1%) 2,549.3 (28.1%)
≥$60,000 332.4 (8.7%) 239.4 (14.7%) 53.1 (10.2%) 152.7 (13.1%) 2,666.5 (29.4%)
Sepsis-associated conditions, 10

3
(% of admissions)
Chronic liver disease 81.8 (2.1%) 48.5 (2.9%) 14.9 (2.8%) 26.4 (2.2%) 90.5 (1.0%)
Hematologic malignancy 28.5 (0.7%) 21.0 (1.3%) 4.4 (0.8%) 5.9 (1.1%) 105.0 (0.5%)
Non-hematologic malignancy 129.5 (3.3%) 77.1 (4.6%) 18.3 (3.4%) 31.5 (2.6%) 522.5 (5.6%)
End-stage renal disease 17.5 (0.4%) 44.4 (2.7%) 12.8 (2.4%) 2.6 (0.3%) 24.1 (0.2%)
HIV 59.7 (1.5%) 27.5 (1.6%) 10.5 (2.0%) 11.0 (0.9%) 24.3 (0.3%)
Alcohol dependence 134.1 (3.4%) 53.6 (3.2%) 18.6 (3.5%) 87.1 (7.2%) 165.0 (1.8%)
Organ transplantation 13.4 (0.3%) 67.2 (4.0%) 11.5 (2.1%) 1.4 (0.1%) 51.6 (0.6%)
Infection due to device 9.2 (0.2%) 14.0 (0.8%) 4.0 (0.8%) 1.7 (0.1%) 22.7 (0.2%)
Red blood cell transfusion 130.3 (3.3%) 93.6 (5.6%) 30.1 (5.6%) 41.2 (3.4%) 304.3 (3.3%)
Co-morbidity index (Charlson-Deyo) categories, 10
3
(% of admissions)
0 points 2,650.5 (67.6%) 588.4 (35.1%) 198.5 (37.0%) 818.2 (69.5%) 6,439.0 (67.2%)
1 point 631.0 (16.1%) 451.4 (27.0%) 148.0 (27.6%) 248.4 (16.3%) 1,508.2 (20.4%)
2 to 8 points 616.8 (15.7%) 617.5 (36.9%) 186.1 (34.6%) 147.3 (13.6%) 1,259.9 (12.1%)
9 or more points 22.3 (0.6%) 16.6 (1.0%) 4.5 (0.8%) 4.3 (0.6%) 53.5 (0.4%)
Sepsis-associated admissions, 10
3
Sepsis (% of admissions) 75.3 (1.9%) 76.2 (4.6%) 25.0 (4.6%) 18.8 (1.5%) 127.3 (1.4%)
Severe sepsis (% of sepsis admissions) 41.0 (54.5%) 47.3 (62.1%) 15.5 (62.0%) 9.2 (48.8%) 58.1 (45.6%)
Septic shock (% of sepsis admissions) 10.6 (14.1%) 11.1 (14.6%) 3.4 (13.8%) 2.7 (14.6%) 17.7 (13.9%)
The study cohort was divided into age strata based on age qualification for Medicare. Insurance categories were determined based on primary and secondary
payers identified by the data source (see Methods). Numbers represent totals from the full weighted sample and are presented as factors of 10
3
. Percentages are
based on insurance category by age stratum (unless otherwise indicated). Categorization of co-morbidity index was based upon preliminary analyses examining
best fit with odds of sepsis. Severe sepsis and septic shock was categorized as a sepsis-associated admission with ICD-9 codes for any organ failure or for shock,
respectively.

O’Brien et al. Critical Care 2011, 15:R130
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Insurance category and sepsis-associated mortality
Table 5 shows the age-strata-specific discharge disposi-
tion and h ospital length of stay by insurance category.
In both age strata, uninsured sepsis patients were most
likely to die during hospitalization and least likely to be
discharged to an intermediate/skilled nursing facility.
Hospital length of stay was longest among Medicaid
patients in both age strata.
The unadjusted and risk-adjusted odds of hospital
mortality among sepsis patients are shown in Table 6.
Among those 18 to 64 years, there was a significantly
higher risk-adjusted odds of sepsis-associated mortality
among uninsured patien ts (AOR 1.45, P < 0.0001) and
among patients with Medicaid (AOR 1.17, P < 0.0001),
compared to those with private insurance. An increased
unadjusted odds of sepsis-associated mortality among
Table 2 Insurance category and covariates of interest, 65+ years old
Medicaid Medicare alone Medicaid +
Medicare
Uninsured Private insurance plus
Medicare
Admissions, 10
3
(%) 197.7 (1.6%) 6,696.1 (54.8%) 921.8 (7.6%) 39.4 (0.3%) 4,355.1 (35.7%)
Age, Mean (95% C.I.) 75.1 (74.5 to
75.7)
77.9 (77.7 to
78.0)

77.7 (77.6 to 77.9) 75.2 (74.8 to
75.7)
77.8 (77.6 to 77.9)
Female, 10
3
(% of admissions) 131.4 (66.6%) 3,844.0 (57.4%) 655.1 (71.1%) 22.5 (56.4%) 2,463.3 (56.6%)
Race, 10
3
(% of admissions)
White 47.2 (24.0%) 4,020.8 (60.0%) 374.5 (40.6%) 14.6 (36.6%) 2,579.2 (59.2%)
Black 24.8 (12.5%) 469.5 (7.0%) 164.9 (17.9%) 4.8 (12.1%) 182.4 (4.2%)
Hispanic 59.3 (30.0%) 417.7 (6.2%) 113.7 (12.3%) 9.6 (24.1%) 104.9 (2.4%)
Asian or Pacific Islander 20.7 (10.5%) 133.4 (2.0%) 10.1 (1.1%) 2.0 (4.9%) 19.4 (0.4%)
Native American 0.9 (0.5%) 5.3 (0.1%) 1.9 (0.2%) 0.2 (0.5%) 2.3 (0.1%)
Other 10.0 (5.1%) 70.5 (1.1%) 25.8 (2.8%) 2.9 (7.2%) 66.5 (1.5%)
Missing 34.7 (17.5%) 1,578.8 (23.6%) 231.0 (25.1%) 5.8 (14.6%) 1,400.4 (32.2%)
Quartile of median annual household income by zip code, 10
3
(% of admissions)
<$36,000 75.7 (38.8%) 1,734.4 (26.5%) 433.9 (48.2%) 10.5 (28.0%) 952.2 (22.3%)
$36,000 to <$45,000 52.7 (27.0%) 1,848.2 (28.3%) 217.7 (24.2%) 10.4 (27.9%) 1,116.7 (26.1%)
$45,000 to <$60,000 38.2 (19.6%) 1,640.7 (25.1%) 159.3 (17.7%) 8.7 (23.2%) 1,172.8 (27.4%)
≥$60,000 28.6 (14.6%) 1,318.2 (20.2%) 89.8 (10.0%) 7.8 (20.9%) 1,037.1 (24.2%)
Sepsis-associated conditions, 10
3
(% of admissions)
Chronic liver disease 4.4 (2.2%) 76.8 (1.1%) 11.8 (1.3%) 0.7 (1.7%) 42.1 (1.0%)
Hematologic malignancy 2.5 (1.2%) 124.2 (1.9%) 10.4 (1.1%) 0.4 (1.1%) 90.1 (2.1%)
Non-hematologic malignancy 17.6 (8.9%) 610.0 (9.1%) 58.5 (6.3%) 4.3 (10.8%) 415.4 (9.5%)
End-stage renal disease 3.6 (1.8%) 95.1 (1.4%) 17.2 (1.9%) 0.4 (0.9%) 56.6 (1.3%)

HIV 0.3 (0.2%) 1.9 (0.03%) 0.4 (0.05%) 0.01 (0.02%) 0.4 (0.01%)
Alcohol dependence 1.8 (0.9%) 51.9 (0.8%) 7.3 (0.8%) 0.5 (1.3%) 22.8 (0.5%)
Organ transplantation 0.3 (0.2%) 16.0 (0.2%) 1.3 (0.1%) 0.04 (0.1%) 9.4 (0.2%)
Infection due to device 0.7 (0.3%) 30.6 (0.5%) 4.3 (0.5%) 0.07 (0.2%) 20.1 (0.5%)
Red blood cell transfusion 17.1 (8.7%) 538.0 (8.0%) 87.5 (9.5%) 2.6 (6.5%) 382.9 (8.8%)
Co-morbidity index (Charlson-Deyo) categories, 10
3
(% of admissions)
0 points 49.7 (25.1%) 1,853.2 (27.7%) 192.9 (20.9%) 14.0 (35.0%) 1,301.8 (29.9%)
1 point 60.3 (30.5%) 2,034.6 (30.4%) 288.6 (31.3%) 11.9 (29.7%) 1,313.7 (30.2%)
2 to 8 points 84.8 (42.9%) 2,703.2 (40.4%) 428.6 (46.5%) 13.4 (33.6%) 1,669.3 (38.3%)
9 or more points 3.0 (1.5%) 105.1 (1.6%) 11.8 (1.3%) 0.7 (1.6%) 70.4 (1.6%)
Sepsis-associated admissions, 10
3
Sepsis (% of admissions) 11.4 (5.8%) 288.5 (4.3%) 58.7 (6.4%) 1.5 (3.8%) 163.2 (3.8%)
Severe sepsis (% of sepsis
admissions)
7.2 (62.6%) 154.7 (53.6%) 30.4 (51.8%) 0.9 (60.8%) 81.6 (50.0%)
Septic shock (% of sepsis
admissions)
2.2 (19.0%) 44.5 (15.4%) 8.8 (15.0%) 0.3 (20.3%) 24.1 (14.8%)
The study cohort was divided into age strata based on age qualification for Medicare. Insurance categories were determined based on primary and secondary
payers identified by the data source (see Methods). Numbers represent totals from the full weighted sample and are presented as factors of 10
3
. Percentages are
based on insurance category by age stratum (unless otherwise indicated). Categorization of co-morbidity index was based upon preliminary analyses examining
best fit with odds of sepsis. Severe sepsis and septic shock was categorized as a sepsis-associated admission with ICD-9 codes for any organ failure or for shock,
respectively.
O’Brien et al. Critical Care 2011, 15:R130
/>Page 5 of 11

patients with Medicare was not statistically significant
after risk adjustment. Among patients 65+ years, unin-
sured patients had significan tly higher risk-adjusted
odds of sepsis-associated mortality ( AOR 1.45, P =
0.0048), compared to the reference group. Those with
Medicare alone had significantly lower odds of sepsis-
associated mortality (AOR 0.92, P = 0.0072) but this
association was not statistically significant in the unad-
justed analyses (OR 1.00, P = 0.91).
Uninsured sepsis patients who survived hospitalization
were significantly less likely to be discharged to an
extended care facility than sepsis survivors with private
insurance (Table 5). We tested hypothetical mortality
rates between 10% and 50% among patients discharged
to an extended care facility. For both age strata, the
unadjusted odds of sepsis-associated mortal ity were sig-
nificantly higher among the uninsured, provided less
than 20% of patients discharged to an intermediate/
skilled nursing facility were reclassified as having died.
The point estimates of the o dds ratios for sepsis- related
mortality remained higher in the uninsured patients
until 30% or more of the patients discharged to an inter-
mediate/skilled nursing facility were reclassified as hav-
ing died in both age strata.
To explore the possibility that uninsured patients
received care in hospitals with less experience in caring
Table 3 Sepsis and covariates of interest
No sepsis Sepsis Total
Admissions, 10
6

(%) 27.98 (97.1%) 0.85 (2.9%) 29.84
Age, Mean (95% C.I.) 56.6 (56.2 to 57.0) 67.3 (66.9 to 67.7) 56.5 (56.1 to 56.9)
Female, 10
6
(% of admissions) 17.52 (62.8%) 0.45 (52.8%) 17.96 (62.5%)
Race, 10
6
(% of admissions)
White 14.14 (50.5%) 0.42 (49.5%) 14.56 (50.5%)
Black 2.81 (10.0%) 0.11 (13.4%) 2.93 (10.2%)
Hispanic 2.41 (8.6%) 0.07 (8.2%) 2.48 (8.6%)
Asian or Pacific Islander 0.48 (1.7%) 0.02 (2.2%) 0.50 (1.7%)
Native American 0.04 (0.1%) 0.001 (0.2%) 0.04 (0.1%)
Other 0.56 (2.0%) 0.01 (1.6%) 0.57 (2.0%)
Missing 7.54 (27.0%) 0.21 (24.8%) 7.75 (26.9%)
Quartile of median annual household income by zip code, 10
6
(% of admissions)
<$36,000 7.51 (27.5%) 0.25 (30.0%) 7.76 (27.5%)
$36,000 to <$45,000 7.26 (26.5%) 0.22 (26.1%) 7.47 (26.5%)
$45,000 to <$60,000) 6.83 (25.0%) 0.20 (24.0%) 7.02 (24.9%)
≥$60,000 5.76 (21.1%) 0.16 (19.9%) 5.93 (21.0%)
Sepsis-associated co-morbidities, 10
3
(% of admissions)
Chronic liver disease 367.3 (1.3%) 30.5 (3.6%) 397.8 (1.4%)
Hematologic malignancy 350.4 (1.3%) 42.0 (5.0%) 392.4 (1.4%)
Non-hematologic malignancy 1,800.5 (6.4%) 84.2 (9.9%) 1,884.7 (6.5%)
End-stage renal disease 244.8 (0.9%) 29.3 (3.5%) 274.1 (1.0%)
HIV 123.1 (0.4%) 13.0 (1.5%) 136.1 (0.5%)

Alcohol dependence 528.4 (1.9%) 14.3 (1.7%) 542.8 (1.9%)
Organ transplantation 157.4(0.6%) 14.8 (1.8%) 172.3 (0.6%)
Infection due to device 88.6 (0.3%) 18.7 (2.2%) 107.4 (0.4%)
Red blood cell transfusion 1,484.3 (5.3%) 143.2 (16.9%) 1,627.5 (5.6%)
Co-morbidity index (Charlson-Deyo) categories, 10
6
(% of admissions)
0 points 13.89 (49.6%) 0.22 (26.0%) 14.11 (48.9%)
1 point 6.47 (23.1%) 0.22 (26.4%) 6.70 (23.2%)
2 to 8 points 7.34(26.2%) 0.39 (45.7%) 7.73 (26.8%)
9 or more points 0.28(1.0%) 0.02 (1.9%) 0.29 (1.0%)
Number of organ failures, 10
6
(% of admissions)
None 24.63 (88.1%) 0.40(47.3%) 25.04 (86.9%)
One 2.75 (9.8%) 0.25 (29.6%) 3.00 (10.4%)
Two or more 0.59 (2.1%) 0.20 (23.1%) 0.78 (2.7%)
Numbers represent totals from the full weighted sample. Numbers are presented as factors of 10
3
or 10
6
as indicated. Categorization of co-morbidity index was
based upon preliminary analyses examining best fit with odds of sepsis.
O’Brien et al. Critical Care 2011, 15:R130
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for sepsis or with poorer overall outcomes from sepsis,
we placed hospitals into groups based on quartiles of
either sepsis-associated admission rate (for example, the
percentage of admissions involving sepsis) or sepsis-
associated mortality rate (for example, the percentage of

sepsis patients dying in the hospital), respectively. This
resulted in a significant trend over the lowest, middle
and highest groups of hospitals based on sepsis-asso-
ciated admission rates (1.4% vs. 2.5% vs. 4.0% sepsis-
associated hospitalizations, respectively, P < 0.0001 by
Cochrane-Armitage trend test) and based on sepsis-
associated mortality rates (12.6% vs. 19.6% vs. 27.6%
mortality among sepsis patients, respectively, P <
0.0001). There was a significant trend of uninsured
Table 4 Unadjusted and risk-adjusted association between insurance category and sepsis-associated hospitalization by
age strata
Unadjusted P-value Adjusted P-value
18 to 64 years
Medicaid 1.40 (1.34 to 1.48) <0.0001 1.50 (1.44 to 1.56) <0.0001
Medicare 3.42 (3.25 to 3.61) <0.0001 1.96 (1.86 to 2.03) <0.0001
Medicaid + Medicare 3.50 (3.26 to 3.75) <0.0001 2.22 (2.10 to 2.35) <0.0001
Uninsured 1.13 (1.06 to 1.20) 0.0003 1.18 (1.12 to 1.24) <0.0001
Private insurance Reference Reference
65+ years
Medicaid 1.58 (1.44 to 1.73) <0.0001 1.43 (1.32 to 1.55) <0.0001
Medicare alone 1.16 (1.10 to 1.22) <0.0001 1.13 (1.08 to 1.19) <0.0001
Medicaid + Medicare 1.75 (1.64 to 1.86) <0.0001 1.62 (1.54 to 1.71) <0.0001
Uninsured 1.02 (0.88 to 1.18) 0.82 1.04 (0.90 to 1.20) 0.63
Private insurance plus Medicare Reference Reference
The study cohort was split into age strata based on age qualifications for Medicare. The risk-adjusting model included demographic information, sepsis-
associated co-morbidities, and categorized Charlson-Deyo score (see Methods for details).
Table 5 Discharge disposition and hospital length of stay among sepsis patients by insurance category and age strata
Discharge disposition, 10
3
(%) Hospital length of stay, Days, Mean (95% C.

I.)
Died Skilled/intermediate nursing
facility
Home
18 to 64 years
All 46.1 (14.4%) 64.1 (20.0%) 210.7
(65.7%)
13.7 (13.3 to 14.1)
Medicaid 11.9 (15.8%) 17.5 (23.4%) 45.7 (60.8%) 15.2 (14.7 to 15.8)
Medicare 11.2 (14.8%) 20.0 (26.5%) 44.5 (58.8%) 13.4 (13.0 to 1.38)
Medicaid + Medicare 3.4 (13.7%) 7.9 (32.2%) 13.3 (54.2%) 13.1 (12.7 to 13.6)
Uninsured 3.0 (16.2%) 1.8 (9.5%) 13.9 (74.3%) 12.8 (12.2 to 13.4)
Private insurance 16.7 (13.1%) 16.8 (13.3%) 93.2 (73.6%) 13.1 (12.6 to 13.7)
65+ years
All 128.1
(24.6%)
202.8 (39.0%) 189.0
(36.4%)
11.4 (11.1 to 11.7)
Medicaid 3.1 (26.9%) 4.0 (34.7%) 4.4 (38.4%) 15.2 (14.3 to 16.1)
Medicare alone 70.2 (24.4%) 113.3 (39.4%) 103.8
(36.1%)
11.3 (11.0 to 11.5)
Medicaid +Medicare 14.8 (25.4%) 27.9 (48.0%) 15.4 (26.5%) 11.6 (10.8 to 12.4)
Uninsured 0.5 (32.2%) 0.3 (16.5%) 0.8 (51.3%) 12.1 (10.5 to 13.8)
Private insurance plus
Medicare
39.6 (24.5%) 57.5 (35.6%) 64.6 (40.0%) 11.2 (10.8 to 11.6)
The study cohort was divided into age strata based on age qualification for Medicare. Insurance categories were determined based on primary and secondary
payers identified by the data source (see Methods). Insurance categories for admissions among those 18 to 64 years old and 65+ years old were identical except

the “Medicare” and “Private” categories. Among those <65 years old, those with Medicare with or without Private insurance were categorized as “Medicare.”
Those with private insurance without Medicare were then categorized as “Private.” Among those 65+ years, only those with Medicare and no secondary payer
were categorized as “Medicare.” Those with Medicare and private insurance were categorized as “Private Insurance plus Medicare.” Numbers represent totals
from the full weighted sample and are presented as factors of 10
3
. Percentages are based on insurance category by age stratum. Discharge disposition was
categorized from the discharge record (see Methods for details).
O’Brien et al. Critical Care 2011, 15:R130
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admissions to hospitals categorized by sepsis-associated
admission rates (4 .2% of admissions in lowest quartile,
4.3% in middle quartiles, 4.8% in highest quartile hospi-
tals, P < 0.0001 by Cochrane-Armitage trend test) and
when categorized by sepsis-associated mortality rates
(3.4% of admissions in lowest quartile hospitals, 4.4% in
middle quartile hospitals, 4.8% in highest quartile hospi-
tals, P < 0.0001 by Cochrane-Armitage trend test).
When the risk adjusting regressions were refit to the
age-stratum within each hospital group, the odds of sep-
sis-associated mortality remained elevated for the unin-
sured patients compared to the reference group (Table
7). In the older age stratum, not all analyses were statis-
tically significant but the point estimate was similar to
that found for the overall cohort.
Discussion
In this retrospective cohort study, the risk-adjusted odds
of a sepsis-associated admission were significantly
increased among those with Medicare and/or Medicaid
in a younger (18 to 64 years) and older (65+ years) age
stratum, compared to those w ith private insurance.

Uninsured patients in the younger age stratum also had
higher risk-adjusted odds of sepsis-associated hospitali-
zation. We also found consistently increased odds of
sepsis-associated mortality among uninsured patients,
compared to those with private insurance.
In the United States, insurer is a complex construct
determined by age, chronic health conditions, employ-
ment status, income level, state of residence and other
factors. Barriers to health care that might prevent sepsis
(for example, immunizations) are likely to be different
among patients with private insurance compared to
those with Medicare compared to those with Medicaid
compared to those with no insurance. Mechanisms
related to social disadvantages related to a lack of pri-
vate insurance are likely co ntributors to the observed
results, including those resulting from a lack of
Table 6 Unadjusted and risk-adjusted association between insurance category and sepsis-associated mortality by age
strata
Unadjusted P-value Adjusted P-value
18 to 64 years
Medicaid 1.24 (1.15 to 1.33) <0.0001 1.17 (1.08 to 1.26) <0.0001
Medicare 1.14 (1.08 to 1.22) <0.0001 1.04 (0.97 to 1.12) 0.24
Medicaid + Medicare 1.05 (0.95 to 1.15) 0.36 1.07 (0.97 to 1.18) 0.19
Uninsured 1.28 (1.16 to 1.41) <0.0001 1.45 (1.29 to 1.62) <0.0001
Private insurance Reference Reference
65+ years
Medicaid 1.13 (0.98 to 1.31) 0.09 0.99 (0.87 to 1.13) 0.90
Medicare alone 1.00 (0.94 to 1.06) 0.91 0.92 (0.86 to 0.98) 0.0072
Medicaid + Medicare 1.05 (0.99 to 1.12) 0.12 1.06 (1.00 to 1.13) 0.07
Uninsured 1.47 (1.15 to 1.86) 0.0018 1.45 (1.12 to 1.89) 0.0048

Private insurance plus Medicare Reference Reference
The study cohort was split into age strata based on age qualifications for Medicare. The risk-adjusting model included demographic information, categorized
Charlson-Deyo score, number of dysfunctional organ systems, and sepsis-associated co-morbidities which met a priori criteria for inclusion, (see Methods for
details).
Table 7 Sepsis-associated mortality among uninsured patients, stratified by hospital-based rates of sepsis-associated
admission or sepsis-associated mortality
Age
stratum
Total
cohort
Sepsis-associated admission rate Sepsis-associated mortality rate
Admissions to
hospitals in
lowest quartile
Admissions to
hospitals in
middle quartiles
Admissions to
hospitals in
highest quartile
Admissions to
hospitals in
lowest quartile
Admissions to
hospitals in
middle quartiles
Admissions to
hospitals in
highest quartile
18 to

64 years
1.45
(1.29 to
1.62)
3.76 (2.52 to 5.63) 1.36 (1.19 to 1.57) 1.49 (1.21 to 1.83) 1.53 (1.12 to 2.08) 1.53 (1.34 to 1.74) 1.27 (1.04 to 1.54)
65+
years
1.46
(1.12 to
1.89)
8.67 (2.33 to 32.33) 1.37 (0.98 to 1.90) 1.52 (0.96 to 2.40) 1.59 (1.06 to 2.39) 1.33 (0.90 to 1.97) 1.62 (1.11 to 2.36)
Hospitals were divided into categories by percentage of admissions involving sepsis ("sepsis-associated admission rate”) and by percentage of sepsis-associated
admissions dying in the hospital ("sepsis-associated mortality rate”). Hospitals were divided into quartiles and the middle two quartiles were combined. The
adjusted odds ratios (95% confidence intervals) are referent to patients with any private insurance and adjusted for covariates included in the final risk-adjusting
age-strata specific models (see Methods for details).
O’Brien et al. Critical Care 2011, 15:R130
/>Page 8 of 11
commercial insurance (for example, less access to care)
or leading to a lack of commercial insur ance (for exam-
ple, unemployment). However, we cannot exclude con-
tributions from the actual mechanism of health care
reimbursemen t and its associated benefits (for examp le,
wellness programs). Differences in co-morbidities not
currently known to be associated with sepsis, in socioe-
conomic status, in environmental and genetic factors
and provided care, both before, during and after sepsis
may be additional factors which could account for some
of the observed disparities between insurance categories.
Regardless of the mechanism, the finding of a higher
unadjusted rate of sepsis-associated admissions, a diag-

nosis which consumes significant health care resources
[1], may be enough of an incentive to prompt greater
attention on the care and outcome of Medicare and
Medicaid patients with sepsis.
The specific reasons for greater risk-adjusted odds of
sepsis-associated hospitalizations among adults without
private insurance are uncertain but could include resi-
dual confounding by co-morbidities, disability and frailty
not fully adjusted in our analyses. We stratified our ana-
lyses by age to account for some of the differences in
qualifying criteria for certain insurance types (for exam-
ple, age alone qualifies those 65+ for Medicare while
younger patients must be permanently disabled, have
end-stage renal disease, and so on). An inability to
account for some of these differences (for example,
frailty) may be responsible for the difference in magni-
tude of association between Medicare and sepsis among
the younger (AOR 1.96) and the older strata (AOR
1.13). The NIS is abstracted from records of hospitaliza-
tions and is not a true population-based database.
Therefore, the increased odds of sepsis are most purely
interpreted as increased odds of hospitalization with
sepsis compared to hospitalization for reasons other
than sepsis. An alternate interpretation of our d ata is
that those with private insurance are more likely to be
hospitalized for non-sepsis indications, potentially repre-
senting a healthy user bias [19], a possibility not
excluded in the current analyses. However, the finding
of a similar percentage of admissions associated with
sepsis among uninsured patients and those with private

insurance in the younger (1.5% vs. 1.4% of admissions,
respectively) and older age strata (3.8% vs. 3.8% of
admissions, respectively) is reassuring. Sepsis could also
occur at a similar rate among all patients but patients
without private in surance have more severe disease and/
or greater access to care, resulting in higher rates of
hospitalization.
Uninsured patients had higher risk-adjusted odds of
sepsis-associated mortality. Among those 18 to 64 years,
patients with Medicaid also had significantly higher risk-
adjusted odds of sepsis-associated mortality, but this
was of a smaller magnitude than seen for uninsured
patients. While unproven by the available data, it is pos-
sible that these patients delay care for sepsis. Perhaps
supporting such an explanation is the finding of an
increased rate of severe sepsis and septic shock among
uninsured and Medicaid patients with sepsis compared
to those with private insurance. While we adjusted for
numbers of organ failures, using administrative data pre-
vented the use of a physiology-based severity of illness
system that might provide greater detail r egarding this
observation. Multiple studies have reported higher risk-
adjusted mortality for critically ill patients without
insurance [18,20 -23]. To our knowledge, this is the first
such study specifically examining this association among
sepsis patients. Limitations to these findings are our
inability to precisely identify the mechanism of increased
sepsis-related mortality among the uninsured and to
assess the severity, stability and treatment of co-morbid-
ities which could have affected survival among unin-

sured sepsis patients. It is also possible that in some
hospitals, patients initially admitted without insurance
may be moved to the Medicaid gro up to improve hospi-
tal reimbursement. If this occurred in a systematic man-
ner (for example, those living for only a short time with
sepsis do not have the required paperwork completed
and die as uninsured while those living longer receive
Medicaid), this could bias the observed results. Among
the older age stratum, patients with Medicare had lower
risk-adjusted odds of sepsis-associated mortality com-
pared to patients with Medicare and private insurance.
The magnitude of this association was relatively small
and only found in the risk-adjusted analyses, raising
questions about the clinical significance and validity of
this finding.
We found that uninsured patients were significantly
more likely to receive care in hospitals with higher sep-
sis-associated admission rates and in hospitals with
higher sepsis-related mortality rates. Any hospital-based
effect (for example, higher mortality d ue to poorer care
for seps is patients) would likely affect all sepsis patients
at that hospital and, therefore, would be accounted for
in the stratification analysis. We found no evidence of
such an effect. Our findings do not, however, eliminate
the possibility of differences in care for uninsured
patients relative to those with private insurance across
all hospitals, delays in presentation for treatment of sep-
sis, and inadequate pre-sepsis treatment of known sepsis
risk-factors leading to more severe disease a s possible
mechanisms for the observed association. Finally, while

uninsured patients were less likely to be discharged to
intermediate/skilled nursing facilities, more than 20% of
patients would have to be reclassified as dying, rather
than being discharged to such facilitie s, to confound the
observed findings. While this mortality rate may seem
O’Brien et al. Critical Care 2011, 15:R130
/>Page 9 of 11
realistic for sepsis survivors discharged to such a facility,
thiswouldhavetobethemortalityrateoverashort
interval - namely, during the time that a privately
insured patient would have remained hospitalized if she
were uninsured (on average, less than one day for the
older cohort). Also, a similar length of stay among unin-
sured sepsis patients and those with private insurance
argues against a significant discharge bias.
Limitations
Primary among the limitations of this study is the use of
an administrative databa se that lacks independen t valida-
tion with the clinical record and relies on billing codes.
We cannot, for example, determine if sepsis was the pri-
mary reason for admission or was a nosocomial complica-
tion. In the case of sepsis-associated mortality, we cannot
determine that sepsis was the actual cause of death.
Instead, patients could survive sepsis and die of an alter-
nate cause and yet be considered a sepsis-associated death.
Because sampling in NIS is not directly based upon the
mix of insurance types, there is the possibility of selection
bias for certain types of insurance that could make the
observed estimates of association less accurate. Bias in the
observed results would likely require a systematic miscod-

ing of sepsis and/or seps is-associated mortality based on
insurance category. For example, if those abstracting
charts of patients with private insurance were more likely
to code for sepsis than those abstracting charts of patients
with Medicaid and/or Medicare, the observed results
could be biased. For the purposes of assessing the
mechanism(s) of the observed associations, the data
included in NIS a re limited. For example, while quartiles
of median income based on zip code have been used as a
surrogate for socioeconomic status [24], it remains a crude
surrogate for this construct. We excluded records of
patients transferred from or to another short-term acute
care hospital to reduce the likelihood of transfer bias and
double counting individual patients [6]. However, if there
was a disparity in the transfe r of sepsis versus non-sepsis
patients based on insurance, our observed results may suf-
fer from selection bias.
While not the primary focus of the current study, our
incidence rates of sepsis should best be interpreted a s
“treated incidence” [25]. This requires the recognition of
sepsis and the hospitali zation of the patient so that the
record is included in the database. Considering the low
rate of recognition of sepsis by clinicians [26], including as
a cause of death [27], and the insensitive nature of diag-
nostic codes for sepsis [8], our reported numbers of sepsis
cases may be an underestimate of the true incidence.
Conclusions
Using a national discharge database, we found higher
risk-adjusted odds of a sepsis-associated
hospitalization among patients with Medicare and/or

Medicaid, compared to those with private insurance.
Younger (18 to 64 years) uninsured patients also had
higher risk-adjusted odds of sepsis-associated admis-
sions and uninsured sepsis patients in both age strata
were more likely to die during hospitalization. While
these results provide initial insight into the associa-
tion between sepsis and insurance category, the speci-
fic mechanisms of these associations cannot be
definitively determined from the existing data. A pro-
spective, population-based study with longitudinal
patient-level information on outpatient care prior to
the sepsis admission and inpatient care would allow
for a better assessment of additional risk factors for
sepsis and sepsis-associated mortality and provide tar-
gets for intervention that might mitigate the observed
disparities.
Key messages
• Sepsis is a common reason for hospitalization and
is involved in approximately one in four deaths
among hospitalized patients.
• Among those under 65 years old, patients without
private insurance have significantly higher odds of
sepsis-associated hospitalization with the highest
odds among those with Medicare with or without
Medicaid.
• Among those age 65+, patients with Medicaid with
or without Medicare had the highest risk-adjusted
odds of sepsis-associated hospitalization.
• Among those with sepsis, uninsured patients have
higher odds of hospital mortality compared to those

with private insurance.
• Higher sepsis-associated mortality among unin-
sured patients is not explained by examined demo-
graphics, co-morbidities, sepsis-associated organ
failures, socioeconomic factors or differences in
hospitals.
Abbreviations
AOR: adjusted odds ratio; CPT: current procedural terminology codes; NIS:
nationwide inpatient sample; OR: odds ratio.
Acknowledgements
These data were presented in part in an abstract form at the 2008 American
Thoracic Society Conference. As a result of that abstract, summary statistics
were included in a systematic review (see reference 18). The work was
performed at The Ohio State University Medical Center and the Ohio State
University College of Public Health.
Author details
1
Department of Internal Medicine, Division of Pulmonary, Allergy, Critical
Care and Sleep Medicine, Center for Critical Care, The Ohio State University
Medical Center, 201 Davis HLRI, Columbus, OH 43221, USA.
2
College of
Public Health, The Ohio State University, 320 West 10th Avenue, B-110
Starling Loving Hall, Columbus, OH 43221, USA.
3
Department of Medicine,
Division of General Medicine, Universi ty of Michigan, 300 North Ingalls, 7C27,
Ann Arbor, MI 48109, USA.
O’Brien et al. Critical Care 2011, 15:R130
/>Page 10 of 11

Authors’ contributions
JO contributed to the conception, design, statistical analysis and
interpretation of the study and drafting, critical revision, reading and
approval of the manuscript. BL contributed to the design, statistical analysis
and interpretation of the study and critical revision, reading and approval of
the manuscript. NA contributed to the design and interpretation of the
study and drafting, critical revision, reading and approval of the manuscript.
DL contributed to the conception, design, and interpretation of the study
and critical revision, reading and approval of the manuscript. SA contributed
to the design and interpretation of the study and drafting, critical revision,
reading and approval of the manuscript. SL contributed to the design,
statistical analysis and interpretation of the study and critical revision,
reading and approval of the manuscript. All authors read and approved the
final manuscript.
Competing interests
JO is supported by the Davis/Bremer Medical Research Grant and NIH K23
HL075076. The fu nders had no role in study design, data collection and
analysis, decision to publish, or preparation of the manuscript. JO gave a
lecture related to sepsis as a result of an unrestricted grant from BRAHMS,
Inc. He donated the honorarium to the Sepsis Alliance and received airfare
and two nights’ hotel accommodations totaling approximately $1,500 (2009).
JO serves on the Board of Directors for the Sepsis Alliance, a not-for-profit
organization dedicated to improving awareness and care of septic patients.
He is not paid for this directorship.
The other author s all declare that they have no competing interests.
Received: 6 July 2010 Revised: 28 March 2011 Accepted: 23 May 2011
Published: 23 May 2011
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doi:10.1186/cc10243
Cite this article as: O’Brien et al.: Insurance type and sepsis-associated
hospitalizations and sepsis-associated mortality among US adults: A
retrospective cohort study. Critical Care 2011 15:R130.
O’Brien et al. Critical Care 2011, 15:R130
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